How do you connect Spring Boot to a database?

To connect Spring Boot to a database, follow these steps:

1. Add Dependencies:
   • For JPA (e.g., MySQL, PostgreSQL), add the spring-boot-starter-data-jpa dependency.
   • For Database driver (e.g., MySQL, H2), add the corresponding database driver dependency (e.g., mysql-connector-java).

   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-jpa</artifactId>
   </dependency>
   <dependency>
       <groupId>mysql</groupId>
       <artifactId>mysql-connector-java</artifactId>
   </dependency>
   

2. Configure Database Connection:
   • In application.properties or application.yml, set the database connection details (URL, username, password, dialect).

   spring.datasource.url=jdbc:mysql://localhost:3306/mydb
   spring.datasource.username=root
   spring.datasource.password=root
   spring.jpa.hibernate.ddl-auto=update
   spring.jpa.database-platform=org.hibernate.dialect.MySQL5Dialect
   

3. Create Entity Classes:
   • Define your model classes with @Entity and map them to your database tables.

   @Entity
   public class User {
       @Id
       @GeneratedValue(strategy = GenerationType.IDENTITY)
       private Long id;
       private String name;
       // getters and setters
   }
   

4. Create Repository:
   • Use Spring Data JPA’s JpaRepository to perform CRUD operations.

   public interface UserRepository extends JpaRepository<User, Long> {
   }
   

5. Service Layer:
   • In the service layer, inject the repository and use it to interact with the database.

   @Service
   public class UserService {
       @Autowired
       private UserRepository userRepository;
   
       public List<User> getAllUsers() {
           return userRepository.findAll();
       }
   }
   

In summary, Spring Boot simplifies database integration by automatically configuring a connection and providing tools like JPA to easily interact with the database using simple annotations.